1. Field of the Invention
The present invention relates to a method for providing a progressive download service for a playback apparatus supporting a BD-J specification, and more particularly to a method for providing a progressive download service for a playback apparatus supporting a BD-J specification wherein a standby time and a communication overhead necessary for receiving and playing a A/V data by a playback apparatus supporting a BD-J specification are minimized by dividing and receiving the A/V data according to a size of clips using a clip division information.
2. Description of the Related Art
A Blu-ray specification is designed by Blu-ray Disc Association (“BDA”), whose members include Sony, Hitachi and Sharp. The Blu-ray specification includes a specification of a Blu-ray disk which is an optical disc that may be read and recorded using a blue laser.
While a diameter and a thickness of the Blu-ray disk, which are 12 cm and 1.2 mm, respectively, are same as those of conventional CD (Compact Disc) and DVD (Digital Versatile Disc), a storage capacity thereof is larger than those of the conventional CD and DVD.
Because the blue laser having a wavelength of 405 nm is used for reading the Blu-ray disk instead of a red laser having a wavelength of 650 nm used for reading the DVD, more data can be stored in the Blu-ray disk than the DVD.
Specifically, a single layer Blu-ray disk is capable of storing up to 25 GB of a data and a dual layer Blu-ray disk is capable of storing up to 50 GB of the data. This means that the Blu-ray disk can store five times more data than the DVD.
Moreover, a quad layer Blu-ray disk and an octal layer Blu-ray disk can store up to 100 GB and 200 GB, respectively.
The Blu-ray disk supports a video compression codec of MPEG-2 which is widely used in the DVD. Moreover, BDA standard specification requires the Blu-ray disk to use H.264/AVC or VC-1 as the video compression codec which provides improved compression ratio compared to MPEG-2.
In addition, the Blu-ray disk supports audio formats such as Dolby Digital Plus, Dolby TrueHD and DTS-HD Master Audio as well as PCM (Pulse-code modulation), Dolby Digital and DTS.
A Blu-ray player supporting a BD-J specification supports an interactive service based on JAVA. Moreover, the Blu-ray player supporting the BD-J specification supports a network connectivity, a PIP (Picture-In-Picture) and a connection to a local storage.
A Blu-ray player supporting a BD-Live specification is capable of playing the streaming data received through a network communication in addition to the above-described capabilities.
A Virtual File System (“VFS”) enables a playback of the streaming data which is not stored in the Blu-ray disk. Specifically, the VFS configures a virtual package on the Blu-ray player to enable the Blu-ray player to play the streaming data received through a USB port or the network communication as if the streaming data is stored in the Blu-ray disk.
Hereinafter, “a playback apparatus supporting the BD-J specification” includes the Blu-ray player supporting the BD-J specification or an apparatus using a middleware supporting the BD-J specification such as a TV, a set-top box, a PMP (Portable Multimedia Player), a video game console, a PC (Personal Computer) and a PVR (Personal Video Recorder).
The apparatus using the middleware supporting the BD-J specification is not required to have a Blu-ray disk reading capability.
FIG. 1 is a diagram illustrating a configuration for providing an audio/video data in accordance with a conventional method.
The audio/video data, which will be referred to as A/V data hereinafter, may include one of an audio data, a video data and combinations thereof.
An A/V data providing server generates a BUMF (Binding Unit Manifest File) information, an SF (Signature File) information, a playlist information, a clip information and a movie clip according to the BD-J specification.
The BUMF information defines a configuration of a virtual package in XML (Extensible Markup Language) format. For instance, the BUMF information includes a file name information and a binding information on the movie clip included in the A/V data received from the A/V data providing server.
The SF information is used for verifying a validity of the BUMF information. The SF information uses SHA (Secure Hash algorithm)-1.
The playlist information includes an information on the A/V data to be played. For instance, the playlist information includes a playback sequence information, a PlayItem information and a PlayListMark information of clips #1 through #100.
The clip information includes an information required for playing the movie clip. For instance, the clip information includes a stream format information of the corresponding clip, a number of packets included in the corresponding clip, an encoding specification of the corresponding clip and a time stamp information.
The A/V data included in each of the clips #1 through #100 may be different from one another. However, the clips #1 through #100 may have a same size or a same length which is obtained by dividing one large clip or one long clip into smaller or shorter clips.
The playback apparatus stores in a BUDA (Binding Unit Data Area) the BUMF information, the SF information, the playlist information and the clip information received from the A/V data providing server. The playback apparatus carries out a package update from a disk package to the virtual package based on the BUMF information, the SF information, the playlist information and the clip information stored in the BUDA. That is, the playback apparatus is configured to play the clips #1 through #100 received from the A/V data providing server instead of playing a data stored in the Blu-ray disk.
When a configuration of the playback apparatus is complete, the playback apparatus receives from the A/V data providing server and progressively plays the clips #1 through #100. Specifically, the playback apparatus receives the clips #1 through #100 using a progressive download scheme. For instance, when the playback apparatus starts receiving and finishes receiving the clip #1, the playback apparatus starts playing the clip #1 and starts receiving the clip #2 simultaneously. Moreover, when the playback apparatus finishes receiving the clip #2, the playback apparatus starts playing the clip #2 and starts receiving the clip #3 simultaneously.
However, there are certain disadvantages when the playback apparatus employs the progressive download scheme.
When the number of the clips that are to be played is small, a standby time necessary for downloading the clips increases. For instance, when the clips #1 through #100 having a size of 2 GB in total are to be is received, and a time necessary for downloading each of the clips is 20 seconds, the standby time is about 20 seconds. Moreover, if two clips are buffered by the playback apparatus, the standby time is about 40 seconds. Therefore, when the number of the clips is small, the standby time increases.
Increasing the number of the clips in order to overcome above disadvantages also has some disadvantages.
For instance, when the clips #1 through #1000 having a size of 2 GB in total are to be received, and a time necessary for receiving each of the clips is 2 seconds, the standby time is about 2 seconds.
That is, when the number of the clips is increased, the standby time decreases. However, a size of a clip information increases as the number of the clips is increased. Moreover, a communication overhead increases because a communication should be established between the A/V data providing server and the playback apparatus for every clip.